I bet my mom could have written a similar post about my boyfriends about 15 years ago! I came from a nice family and made straight A's in high school but I brought home the most horrendous guys
For example: my mom caught me corresponding with a boyfriend that was in jail, I dated guys that she had taught (remediation teacher) and had failed a couple of times, tattoos were almost a must, etc. I don't know how my mom and dad put up with it! But, they never, ever, ever discouraged me from dating these guys and got to know each one of them - that I brought home, for who they were and not just what they appeared to be (mostly my mom because my dad was kind of clueless as to what was going on). The guys were always complete gentlemen to my parents and treated me well. I never got into (real) trouble with them although some were definitely a bad influence.
I never lost sight of what I wanted out of life or my future and I attribute that to my parents always being a good influence on me. My mom was always supportive of who I dated as long as I was happy and treated right. She never put down a boyfriend in front of me and even welcomed them in our home and family events if we were dating for a long time. I truly believe that it was because of her accepting them and never pushing me away that her and I have an amazing relationship and in the end I married a wonderful guy that both my mom and dad ADORE.
Hopefully your son is in a phase like I was. Once I got to college I started dating a higher quality of guys and my standards rose significantly. I am glad my parents allowed me to get it out of my system when I was young, and to make those mistakes when I was young, so I wouldn't make even bigger ones (marriage, kids with the wrong guy) when I got older. I know I put my parents through A LOT but I also that it is because of their love and unwavering support that I have an amazing life now.
Good luck with your son